Examples of telecommunications systems include distributed antenna systems (DAS's) and repeaters. The repeaters may be off-air repeaters. It is desirable for telecommunications systems to handle multiple technologies, frequency bands, or operators.
Many conventional platforms are not adapted to be readily configured or modified in the field, especially if the electrical equipment should be protected against water and dust. Off-air repeater installations can involve receiving multiple frequency bands from base stations via one or more donor antennas. The core of an off-air repeater 100 can be the frequency independent, digital main board 102 where RF cards 104 are plugged in (see FIG. 1 and FIG. 2). Each RF card 104 itself comprises the RF interface for converting received analog RF signals from a base station or user equipment into digital signals. The RF cards 104 also convert received digital signals from the digital main board 102 back to analog RF signals that are transmitted to a base station or user equipment. By design, each RF card 104 is tuned to a specific frequency range (e.g., in the GSM 900 band ranging from 880 MHz to 960 MHz) and can include a duplexer for each of the donor and coverage ports of the RF card 104. Each duplexer separates transmit (TX) signals from the receive (RX) signals (e.g., for the GSM 900 band, RX signals in the frequency band from 880 MHz to 915 MHz and TX signals in the frequency band from 925 MHz to 960 MHz). Other parts of each RF card 104 include the final power amplifier in RX and TX chain, which amplify the relevant RF signals to a desired output power. The donor and coverage ports of multiple RF cards 104 are combined into one single donor port 108 and one single coverage port 110 of the repeater 100 using a combiner 106. Off-air repeaters can be installed indoors (e.g., small sized rooms, offices, venues, malls, etc.) and outdoors (e.g., urban, rural, etc.). The output power requirements can vary, depending on the installation environment. To cover the possible installations, at least 3 different output power variants (e.g. 100 milliWatts (mW), 1 Watt (W), and 10 W) need to exist in parallel. Additionally, there are dozens of different frequency/operating bands for wireless communications worldwide, and it is expected that this number is increasing due to the required bandwidth and data throughput needs.
The number of different variants of RF cards (frequency and output power) can be numerous.
FIG. 2 depicts an example of a distributed antenna system (DAS) 200 that includes a master unit 202 and multiple remote units 204. The master unit 202 can be communicatively coupled to one or more base stations 206 by cables or other type of communication medium, including a wireless communication medium. Within the master unit 202, multiple technologies, frequency bands, or operators can be separated, first into transmit (TX) and receive (RX) signals by duplexers 208 included in a point-of-interface (POI) module 210, and then combined and split into several common TX and RX paths by transmit and receive splitter/combining matrices 212. The combined TX signals may be converted into optical signals by optical transceivers (OTRX) 214 and then fed to multiple remote units 204 via fibers 216. In other examples, communication media other than optical can be used. Within each remote unit 204, the optical signals are received and converted back to RF signals by an OTRX 218 in the remote unit 204. Each TX signal can be fed to a final amplifier 220. The individual TX signals can be combined in a multiplexer 222 and output on one or more RF ports 224 to serve the coverage area. Similar processing is performed in the upstream or receive direction.
The point of interface 210 within the master unit 202 is typically frequency dependent and includes gain adjustment elements that typically need to be adapted for the received input power of the respective the base station 206. The remote units 204 may handle multiple frequency band mixes and can be available in different output power classes. This can lead to numerous variants of the master unit 202 and remote units 204.